Make the lye water. Using a digital scale, carefully measure out the lye and water in separate glass containers. Then, slowly add the lye to the water (never the other way around—remember, "snow floats on the lake"). Stir until the lye is fully dissolved. The temperature will rise quickly. Set the lye water in a safe, well-ventilated place to cool. Safety Tip: Be cautious during this step as the mixture releases fumes and can cause burns if spilled.
Melt the oils and shea butter. While the lye solution cools, measure out the coconut oil, olive oil, palm oil, and shea butter. Combine them in a large stainless steel pot and melt over low heat. Heat the oils to a temperature of 130-140°F (54-60°C). Once melted, set the pot aside and allow the oils to cool.
Check temperatures. After about 2 hours, check the temperature of both the lye water and the melted oils. Both should be around 110°F (43°C) for the best results. A range of 100-120°F (38-49°C) is acceptable. If either solution is too warm, allow it to cool further until within this range.
Prep mold and mix-ins. While the solutions are cooling, prepare your soap mold and measure out any fragrance or color additives you plan to use. If using colorants, mix them with a small amount of the melted oils for better blending.
Stick blend to trace. Once both the lye water and oils are at the correct temperature, slowly pour the lye solution into the pot with the melted oils. Use a stick blender to mix the solutions until a thin trace is reached—this is when the soap batter thickens slightly, and a trail of soap remains on the surface for a moment before sinking. This usually takes about 1 minute. If using color or fragrance, add them now and stir by hand until evenly incorporated.
Pour into mold. Immediately pour the soap batter into your prepared mold. Smooth the top with a spoon or spatula. Leave the mold uncovered and allow the soap to cure at room temperature for 24 hours.
Unmold and cut. After 24 hours, carefully unmold the soap and cut it into bars. Allow the bars to cure in a well-ventilated area for at least 3 weeks before use. This curing time allows the soap to harden and makes sure a better-quality bar.